High-speed beetling mill



March 31, 1931. KRAMER I 1,798,886

HIGH SPEED BEETLING MILL Filed July 29. 1929 Patented Mar. 31, 1931 UNITEDSTATES PATENT OFFICE ERWIN KRAMER, OE BERLIN, GERMANY, ASSIGNOR TO THE FIRM l-IARTsToFE METALL AKTIiEIhTGESELLSCI-IIIAFT, OF BERLIN-'COPENICK, GEBIh/[ANY HIGH-SPEED surname MILL Application. filed July 2a, 1929, Serial No. 382,041 and in Germany August as, 1928.

5 beetling members being suitably designed, as

fully dealt with hereinafter."

I am aware of the existing beetling mills, as well as of the existing whirling mills. There are in these latter two shafts rotating in opposite directions and operating memhere, for instance propellers or the like, apt

to produce whirls or eddies. In contradistinction to these known whirling millsthere is in my improved mill only one shaft, as in a beetling mill, and the beetling members are so designed that they act like the propellers or the like of a whirling mill andproduce brisk whirls or eddies which encounter one aaother in a manner fully described hereina er.

The known beetling mills suffer from a rather severe drawback which consists in the air or'other gas or gas mixture enclosed in the casing being driven against the inner wall of the case by the centrifugal force arising during the rotations of the beetling members, in consequence whereof the air or gas rotates in the casing, that is to say, is kept in rotary motion'by the rotating beetling members, so that in front of each of these latter an air or" gas cushion is formed by which the proper disintegration of the respective material is impaired. a a

The just mentioneddrawback is dispensed with in my present improved mill in which the otherwise rotating or circulating air or gas in the casing issubdivided into a plurality of individual currents which tend to circulate in opposite directions but continually intersecting one another and formingin this waywhirls or eddies by which the particles of the material under treatment are pushed onto one another so as to mutually contribute to their disintegration.

The operation proceeds, thus, in this way that the material to be disintegrated is disintegrated first by direct impact with the revolving beetling members, and when this disintegrating process has proceeded so far that the particles willfloat in the air, the

further disintegration to a still finer pulverulent or colloidal state proceedsin a twofold manner, in that the direct action of the beetling members is increased owing to the absence of the above-mentioned air cushions, and in. that the particles impinge upon one another, as already mentioned. The eifect or result is an exceedingly fine reduction of the material to powder, even if this material is a metal, in fact, also steel having a strength of from 80 to 90 kg. can be reduced tocolloidal fineness,and this excellent effect is attained with a remarkable small expenditure of power. In other words: theefiiciency of this improved mill is very great.

This is the more the case as the number of operating members in this mill is smaller than formerly whereby also the weight of the operating members, or the weight of the complete mill, is reduced. This is highly important especially in high-speed mills in that the bearings for the shaft supporting the operating members are preserved, and the life of the mill is prolonged. To judge correctly as regards these points it must be borne in mind that it is hardly possible, if possible at all, to balance the revolving, i. e. operating members of mills of the types mentioned.

Another advantage from which, besides, a prolongation of the lifeof the mill results is this that the shaft bearing theoperating members within the casing can be supported at both its ends which is due to the fact that said-members all revolve in the same direction. The inventionis illustrated diagrammatically and by way of example on the accompanying drawing on which i Fig. 1 is an axial section through a mill designed according to this invention, the means for supporting the casing and for driving the shaft having been omitted, and

Fig. 2 a side-view of one of the operating members.

On the drawing. 1 denotes the mill casing which is completely closed, and is provided with 'two projections 2 and 3, one for the introduction of the material to be treated, as well as for the introduction of the conveying air or other gas or gas mixture, and the other for the discharge of the product which is carried away from the casing by said air, etc. 4 is the shaft to which are attached, in the example shown, two operating members 5 and 6 constituting each two arms extending in opposite directions. These members are so keyed to the shaft as to extend parallel to one another.

The arms operate as beetling arms, and

each of them is serrated on its beet-ling face in the manner shown, in that there are provided projections, resembling ratchet teeth and comprising oblique faces 8 (lefthand beetling member in Fig. 1) and 10 (righthand beetling member inv Fig. 1), which are separated from one another by narrow shoulders 9 extending obliquely with respect to the shaft 4. The obliquity of the faces of the two beetling members is counter to one another, as appears distinctly from Fig. 1. The broken lines in this figure and the arrows indicatethe directionin which the particles encountered bylthe shoulders 9 are propelled further onward by them, the respective directions being determined also by the shape of the interior of the casing at or near the bearings of the shaft, also as distinctly appearing from Fig. 1. The. obliquity of the faces 8 and 10 being very moderate, these faces are able to exert powerful blows upon. the particles they encounter vas they are rapidly revolving. The particles cannot, however, slide along the beetling arms toward the free ends thereof, being always intercepted by the next oblique shoulder 9 and thereby being propelled laterally, as indicated by the above-mentioned broken lines and the arrows. Because of this manner of operation, the acceleration work uselessly spent in beetling mills of the old types is nearly completely utilized. The particles encountered by the beetling arms and receiving their blows are continually propelled away from these arms nearly instantly after the blow, on the shortest way imaginable, and they cannot possibly exert, therefore, the detrimental cushioning efiect decreasing the efficiency of the mill. t Besides, not only the particles of the material are propelled laterally by the shoulders 9, but the amounts of air or gas j-ust encountered by them are also propelled away which greatly increases the efficiency of the mill. In steam-turbine construction it is known to attain a great effect with blades of very small dimensions; just so it is possible to attain a remarkably high efliciency in beetling mills of the present improved design with a suitable plurality of narrow shoulders at the projections of the beetling arms.

I wish it to be understood that the particles of the material under treatment, as well as the air or gas, or gas mixture, do not move ceed more or less obliquely and intersect one another whereby the particles of the material are very intensely agitated and their reduction to a very fine powder is very effectively promoted. This is due also to the fact that just by reason of the whirls or eddies continually intersecting one another the particles are again and again conducted into the path of the beetling members, or their blow faces respectively, so as tobeagai-n and again acted on by them.

I- wish it further to be understood that I do not limit myself to the construction shown in the drawing merely by way of illustration. For instance, the beetling members 5' and 6 maybe disposed at right angles with respect to one another, their number may be in creased, they may be arranged nearer with respect to one another, orin groups, and so on. But. the arrangement shown in the drawing has proved highly effective and sat isfactory, especially if the casing is shaped as shown in Fig. 1, i. e. bulged out at its frontal walls, and the spaces between the beetling members and the casing wall, as well as between themselves, are practically equal. j

I claim:

1. In a high-speed beetling mill, the combination with a closed casing, of a single rotatable shaft journalled in said casing, beetling members carried by said shaft and provided ontheir operating faces with obliquely disposed projections adapted to laterally propeltheparticles impingediupon", theprojeetions ofone of said beetling members being inclined opposite to those. on the adjacent beetli-ng member so as to produce interesecting eddyi-ng currents, said casing having enlargements to provide a free spa for said currents. q

2. Ina high-speed beetling mill, the combination'with a closed casing,.beetling members carried by said shaft, each formed with oppositely extending arms, provided ontheir operating faces with obliquely disposed pro jections adapted to laterallyv propel the per: ticles impinged upon, the projections;v orrone of said beetling members being inclined opposite to those of the adjacent beetling member so as to produce intersecting eddying cur rents, said casing having enlargements to provide a free space for said currents.

3. In a high-speed beetling-mill, the com-.- bination with a closed casing, of a single roitatable shaft journalled in said casing, bee tling members carried by said shatt, each formed with oppositely extending arms pro;-

vided on their operating faces with obliquely disposed teeth-like projections, the obliquity of the projections of one of the beetling melnbers being opposite to the obliquity of the pro jections of the adjacent beetling member so as to produce intersecting eddying currents,

said casing having enlargements to provide a free space for said currents.

4. In a high-speed beetling mill, the combination with a closed casing, of a single rotatable shaft journalled in said casing, beetling members carried by said shaft -provided on their operating faces with obliquely disposed projections adapted to laterally propel the particles impinged upon, the projections of one of said beetling members being inclined opposite to those of the adjacent member so as to produce intersecting eddying currents, the frontal walls of said casing being enlarged to provide a free space for said currents.

5. In a high-speed beetling mill, the combination with a closed casing, of a single rotatable shaft journalled in said casing, beetling members carried by said shaft, each formed with oppositely extending arms provided on their operating faces with obliquely disposed teeth-like projections, the obliquity of the projections of one of said beetling members being opposite to the obliquity of the projections of the adjacent beetling member so as to produce intersecting eddying currents, the frontal walls of said casing being enlarged so as to provide a free space for said currents.

In testimony whereof I aflix my signature.

ERWIN KRAMER. 

